One little problem …

When I saw the water leak inside the Caravel several weeks ago, I knew I was in for it. But I had no idea it was going to be this bad.

You might recall that back in early October we discovered that the fresh water tank in the 1968 Airstream Caravel was seeping water and had damaged part of the Marmoleum floor. This incident put me on Full Alert status, because the trailer had been extensively renovated. The Marmoleum floor covering and the plywood subfloor were pristine, and all the woodwork was made new from birch with my own hands. I had a lot invested in that trailer (both time and money) and the sight of a water leak was a dagger to my heart. Water is the #1 killer of Airstreams.

After freaking out for a few minutes, I removed the dinette to assess the damage. The birch was mostly OK thanks to multiple coats of polyurethane, the Marmoleum was lifted (the underlying adhesive had failed), and the water tank was irreparable. Those of you who have been following this saga know that I tossed the tank and ordered a new one, re-glued the floor and mashed it back down with a few hundred pounds of rocks, and fabricated an aluminum threshold to pin the flooring edge. I also sealed the perimeter of the floor covering with tan silicone caulk. That all went well, and now it’s hard to detect that anything ever happened.

The problem of the past week has been installing the new water tank. I ambitiously ordered a 12x12x48 polyethylene tank, which is slightly larger than the original. This by itself just meant I had to trim a little bit of wood here and there, and fabricate a new piece to hold the tank in place. No big deal. The problem came from my failure to request a vent on the tank.

See, the tank is standard-sized but you can have threaded fittings spin-welded anywhere into it. I requested two on the left side: one large fitting at the top for filling the tank, and one small fitting at the bottom for draining it. Logical, right? So I popped the tank in place, hooked up some hose, and we tried to fill it with water as a test.

With no air vent to release the pressure inside the tank, water wouldn’t go into the tank any faster than a weak dribble. Try to fill any faster and water would just burp out the fill opening all over you. I realized my mistake immediately, but what to do? I could have taken the tank around town and found someone locally with spin-welding capability to have a vent added in, but that seemed like a major hassle. Besides, there was no clearance above the tank to fit a vent on the top. The highest point I could fit a vent was equal to the fill point, which meant that when the tank was full, water would come out the vent. That meant I had to find a way to route the vent tube outside, which likely meant cutting a hole in the trailer somewhere. I wasn’t keen on that.

So thereby began a process of trying to outsmart the laws of nature. I dreamed up all kinds of clever ways to vent the tank at the fill hose where it met the tank. Unfortunately, my clever solutions inevitably resulted in a frothy water/air mixture bubbling up the ad hoc “vent” and plugging it, at which point the tank would have no functioning vent and we’d be back to the original problem. Worse, that plug of water would then be forced up the vent hose (by air pressure building inside the tank) and eventually spit out inside the trailer somewhere.

I literally went to bed at night thinking of ways to solve this problem, and woke up in the morning with fresh ideas—which also didn’t work. Every day I went to the hardware store to buy a handful of brass bits, hoses, PVC pipe, and various other plumbing supplies, which I would assemble in the trailer and test. I now have a small Museum of Failed Plumbing in the trash bin. I actually did design a water/air separator that would have worked, but there wasn’t sufficient clearance above, since the dinette seat covers the entire area.

After three frustrating tries, and about six trips to the hardware store, Eleanor suggested something much more clever. “Why don’t we just turn the tank so the drain is at the top?” I glared at the tank for a moment, and suddenly realized she was on to something. By rotating the tank 180 degrees, the large fill opening would be at the bottom, and the drain would be at the top, thus usable as a vent. There’s no problem filling a tank from the bottom as long as the top of the tank is below the entry point, and with a little plumbing I could also use that same bottom connection as the drain. You can see the solution in the photo.

This works beautifully. Now we can fill the tank as fast as we want. As a bonus I was able to route the vent into the existing floor drain, so I didn’t have to cut a fresh hole in the trailer. (The yellow knob is for draining the tank after a camping trip.)

After this I figured I was home free, but no. The next big surprise was that the new tank bulges when full. I hadn’t anticipated that either. The old tank had thick walls and was essentially rigid, but modern poly tanks are thin-walled and very flexible. When I dry-fitted the wood cover and filled the tank to check for leaks, the wood was forced off by the bulging of the tank.

The solution here was to add reinforcement to the tank cover to resist the weight of 225 pounds of water trying to push the walls out. I could have fabricated a new tank cover to accommodate the bulge, but that would meant a search for 1/4″ birch plywood (much harder to find here in Tucson than in wood-happy Vermont) and a few days of cutting, staining, and finishing. At this point I’d been working on the tank problems for a week and I was looking for a way to get this job done. So I added braces and extra screws and I think it will hold up. If not, I have a backup plan involving some aluminum L-channel.

At this point I think I have about 25 hours of work into this “little problem” caused by the original tank leaking. Admittedly, I didn’t just set out to fix the primary problem. I also wanted to improve a few things along the way, like the floor edge sealing, the threshold, and some woodwork details. But it was amazing how that stupid little leak in the tank ended up taking over my life for the past week.

The furniture is back in the trailer now, but the job’s not done. I want to reduce the weight of the dinette table by routing out some of the underside wood. The table was re-made by some well-meaning friends who used 3/4″ plywood, and as a result the table is so heavy it takes two people to lift it out (to convert to a bed). I also need to sanitize the fresh water system with bleach, and I think I may go find the spot where the plumbing makes a loud vibrating noise when the water pump is running, and find some way to silence it.

Whether I get to those jobs this week or not, the trailer needs to get out of the carport and back into off-site storage soon. The Safari’s floor makeover is languishing until I have more carport space, and the Mercedes 300D wants some love too. I’ve got about another six weeks of really fine Fall weather in Tucson to get my projects done, so there’s no time to waste. I’m just hoping that the next few things go more smoothly than this “little problem” with the Caravel.